How Can Libido Causing Impotence Be Increased?

hi, I'm a 22 year old male with arthritis. I have been taking 20mg of methotrexate on and off since i was 8. My condition is under control, i am very active, and eat pretty healthily. However i have recently noticed a massive decline in labido, resulting in impotence. After reflection on my past i have had problems keeping/getting erect while using condoms. I doubt it is anything psychologically related as i am a very relaxed person in the bedroom and put the issue down to my medication. Do you have any advice? preferably i would like to come off methotrexate as its a pretty horrible drug, but i tend to flare up as a result. Thanks